298 
Journal of Agricultural Research 
Vol. XXIII, No. 5 
favorable constant temperature for the different species varied from 15 0 C. 
for larkspur and poppy seeds to 22.5 0 or 25 0 for petunia seed. Some 
kinds of seed germinated equally well with a wide range of tempera¬ 
tures, while for others there was a very definite temperature optimum. 
For instance, larkspur seed germinated much better at 15 0 , which rep¬ 
resents its optimum, than at 17.5 0 , while belvedere seed germinated with 
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Pig. i.—A verage rates and percentages of germination of two lots of carrot seed under 15 temper¬ 
ature conditions. 
equal completeness and with very little difference in rapidity at any 
temperature from 15 0 to 30°. 
Figure 1, representing the average rates and percentages of germina¬ 
tion of two lots of carrot seeds under 15 temperature conditions, illus¬ 
trates the behavior of those seeds which germinated well at constant 
temperature and were tolerant of a wide range of temperatures. The 
figure shows a retarding effect of very cool or very warm temperatures 
and of alternations of temperature between extremes which are widely 
